call it a day vs discontinue

call it a day and discontinue both are verbs.

Word	Noun	Adjective	Verb	Adverb
call it a day	No	No	Yes	No
discontinue	No	No	Yes	No

As verbs, discontinue is a hypernym of call it a day; that is, discontinue is a word with a broader meaning than call it a day:

Other hypernyms of call it a day include cease, give up, lay off, quit, stop.

call it a day (verb)	discontinue (verb)
stop doing what one is doing	prevent completion
	put an end to a state or an activity
	come to or be at an end